Hi,
Adding the Freon to the system shouldn't have anything to do with the battery. Something is either drawing power all the time, or even something simple like a light is staying on. Lets start simple. Take a look through this link and let me know if there is anything in it that helps.
https://www.2carpros.com/articles/car-battery-dead-overnight
If that doesn't help, let me know if other work was done or anything you can think of that may have caused an issue.
Take care,
Joe
Sunday, June 7th, 2020 AT 7:51 PM